The invention concerns a radial piston pump comprising a rotating pump shaft having a portion that is fixedly attached to an eccentric ring, a needle roller bearing being arranged on an outer peripheral surface of the eccentric ring said needle roller bearing comprising a needle roller bushing having two radially inward directed flanges between which needle rollers that are guided in a cage roll, an outer raceway for the needle rollers being formed by an inner peripheral surface of the needle roller bushing and an inner raceway for the needle rollers being formed by the outer peripheral surface of the eccentric ring a stop washer being arranged on one side between one of the flanges of the needle roller bushing and the eccentric ring, said stop washer overlapping the eccentric ring radially, so that an inseparable assembly is formed, and at least one pump plunger that is arranged in a pump housing and extends radially to the pump shaft being supported through an end face on the needle roller bushing
The invention further concerns a radial piston pump comprising a rotating pump shaft having a portion that is fixedly attached to an eccentric ling, a needle roller bearing being arranged on an outer peripheral surface of the eccentric ring, said needle roller bearing comprising a needle roller bushing having two radially inward directed flanges between which needle rollers that are guided in a cage roll, so that an inseparable assembly is formed, an outer raceway for the needle rollers being formed by an inner peripheral surface of the needle roller bushing and an inner raceway for the needle rollers being formed by the outer peripheral surface of the eccentric ring.
A generic eccentric bearing arrangement of the pre-dated type for a reciprocating piston pump is known from the document DE 198 39 430 A1. As can be seen in FIG. 1 of this document, the eccentric bearing arrangement comprises a drive shaft having a shaft journal on which the eccentric bearing is arranged. The eccentric bearing comprises a needle roller bushing which surrounds the eccentric ring with it two radially inward directed flanges. This is effected on one side through an additional stop washer that is arranged between the eccentric ring and one of the flanges. The needle rollers that are guided in a cage roll in axial direction between the flange of the needle roller bushing and the stop washer, the two raceways for the needle rollers being formed by the inner peripheral surface of the needle roller bushing and the outer peripheral surface of the eccentric ring. A pump plunger mounted for longitudinal displacement in a housing contacts the outer peripheral surface of the needle roller bushing through an end face.
A drawback of this prior art is that the eccentric bearing is susceptible to dust pollution particularly when undergoing high rotary speeds.
It is an object of the invention to provide an improved eccentric arrangement for a radial piston pump.
This and other objects and advantages of the invention will become obvious from the following detailed description.
In a first solution, the invention achieves the above objects by the fact that the stop washer is retained in a circumferential groove of the needle roller bushing arid is surrounded radially by an adjacent one of the flanges of the needle roller bushing, and said stop washer comprises an axially inward open annular groove in which the cage is guided.
The inventive configuration of the eccentric bearing arrangement enables a substantially improved sealing action against dust and dirt particles because due to their relative positions, the eccentric ring, the stop washer and the bearing cage act as a labyrinth seal that prevents the entry of dust and dirt particles into the interior of the bearing. Due to this improved sealing action, the operative life of such a bearing is substantially enhanced.
According to one proposition of the invention, the stop washer may be arranged for free rotation or be firmly fixed in the needle roller bushing According to another proposition of the invention, the flange of the needle roller bushing situated opposite the stop washer comprises an axially inward open annular groove in which the cage is guided. Due to this configuration, the sealing action of the bearing on the side concerned is likewise improved due to the formation of a labyrinth.
According to still another proposition of the invention, as viewed in a longitudinal section, the cage has a reduced radial thickness in the region of the annular grooves. This reduced radial thickness creates in the annular groove of the stop washer and the flange, an enlarged empty space that can be utilized for grease storage.
In a second solution, the invention achieves the above objects by the fact that each of the two ends of the eccentric ring comprises a stepped recess into which the stop washer and an opposite one of the flanges of the needle roller bushing engage. In this case, too, due to the inventive configuration and relative positions of the eccentric ring, the bearing cage and the stop washer, a labyrinth seal is formed that creates a substantially improved protection of the bearing from dirt particles.
In a third solution, the invention achieves the above objects by the fact that the stop washer is retained in a circumferential groove of the needle roller bushing and is surrounded radially by an adjacent one of the flanges of the needle roller bushing, a sliding seal being arranged between the cage and the stop washer and between the cage and an opposing one of the flanges.
In a fourth solution, the invention achieves the above objects by the fact that the stop washer is retained in a circumferential groove of the needle roller bushing and surrounded radially by an adjacent one of the flanges of the needle roller bushing, which flange engages through an axial extension into an axially outward open annular groove of the stop washer, and that end of the eccentric ring that is situated opposite the stop washer comprises an axially outward open annular groove into which an axial extension of the other of the two flanges engages.
In a fifth solution, the invention achieves the above objects by the fact that, adjoining the inner raceway for the needle rollers the eccentric ring comprises on each of its two ends, a radially outward directed extension, and each extension is surrounded by one of the flanges of the needle roller bushing. In this case to, due to the formation of a labyrinth by the extensions of the eccentric ring and the two flanges of the needle roller blushing, an efficient seal is created.
Finally, in a sixth solution, the invention achieves the above objects by the fact that, adjoining the inner raceway for the needle rollers, the eccentric ring comprises on one end, a radially outward directed extension that is surrounded by one of the flanges of the needle roller bushing, while on an opposite end, the eccentric ring comprises a stepped recess into which the other of the flanges of the needle roller bushing engages.
The invention will now be described more closely with reference to the following examples of embodiment and the appended drawings.